I knew a sitting SWO DH who didn’t have a sea service ribbon and transferred before the ship deployed.
Think he ultimately got it on his second DH ride (CG OPS).
I worked with a nuke CPO who had around 14 years in that had no sea service ribbon an minimal underway time, he bounced from prototype to either pre-com units, or to CVN's going into the yards, the only way he finally rec'd a sea service ribbon is they kicked him to the west coast.
I also worked with another CPO that had never stood watch on an operating Nimitz class, he took 2 years to get through school, then was a staff pickup, went to a pre-com, then back to prototype, then to us in the yards, so he had been a surface nuke for about 10 years before he operated a Nimitz class reactor.
There are many nukes who work the system.